Modern heating, ventilating and air conditioning (HVAC) system controllers typically include a setback function. The setback function allows the system operator, e.g. a homeowner, to set a different control temperature for each of several time ranges of the day. Thus, the operator may have a different control temperature upon waking, while leaving the home unoccupied, and for sleeping. Typically during the cooling season the setpoint temperature is higher when the home is unoccupied and lower when the home is occupied. Conversely, during the heating season setpoint temperature is typically lower when the home is unoccupied and higher when the home is occupied. Thus, the setback function is an important aspect of reducing the energy required to cool and heat the home.